1. Field of the Invention
The present invention relates to a fluid circulation device comprising at least one membrane pump for fluid circulation in a given direction, and with a given flowrate, thanks to the to-and-from movements of the membrane that are coordinated with the opening and closing of valves situated upstream and downstream of the rigid cavity within which the membrane moves.
2. Description of the Related Art
The prior art describes numerous membrane pumps that may be separated into two categories: those having a rigid connection between the membrane and its drive system, and those where the membrane is moved via a fluid. This latter solution has the advantage of admitting a membrane change every time the pump is used, and thus avoiding the transmission of polluting or contaminating elements to the fluid pumped. The elasticity of such a connection, to the contrary, has negative effects on the fluid flow precision in each pumping cycle and on its sensitivity to external parameters such as the pressure of the fluid pumped. The prior art more precisely describes numerous systems using pumps having a membrane acted upon by a gas, generally air, so that to-and-from movements of this membrane are created that in alternation, and combined with valve movements, fill and then empty a rigid chamber that is closed off by this soft membrane, thus producing a circulation of the fluid present in the chamber. These pumps as described in the prior art all include a membrane having a flexibility allowing the volume to be varied that is available to produce fluid circulation, one or several valves, as well as a rigid tank set up on the other side of the membrane that takes up the gas intended to actuate said membrane.
From the document U.S. Pat. No. 5,938,634 in particular a system for peritoneal dialysis is known that is driven by variable pressure and includes membrane pumps and valves that are used for the propulsion and directional control of the fluid. From the document U.S. Pat. No. 5,554,011 a membrane pump is known that is actuated by a vacuum and comprises a piston that is subject to the action of a return spring.
The disadvantage of known fluid circulation devices using membrane pumps controlled by a gaseous fluid resides mainly in the difficulty of knowing and determining with precision the quantity or volume of the fluid to be pumped that is displaced in each to-and-from cycle of the membrane. This difficulty arises more particularly from the fact that the volume variation of the air as a compressible fluid used to actuate the membrane does not correspond to the fluid volume to be pumped that is displaced by the membrane, the reasons being compression of the air, the pressure, and the temperatures.